Radio direction indicator system



Dec. 19, 1944. w. P. LEAR 2,365,347

RADIO DIRECTION INDICATOR SYSTEM Original Fi1ed Ju1y 27, 1959 2Sheets-Sheet 1 TO MOTOR CONNECTIONS I VENTOR BY W4 M ,ZQ/ATTORNEY Dec.19, 1944. w p LEAR RADIO DIRECTION INDICATOR SYSTEM 2 Sheets-Sheet 2 TOMOTOR RE LAY CONNECTIONS AZIMUTH COMPENSATOR K INDICATOR Original FiledJuly 27, 1339 TO MOTOR RELAY CONNECTlONS INVENTOR BY Mam ,Z/ATTORNEY Fig4- Patented Dec. 19, 1944 RADIO DIRECTION INDICATOR SYSTEM William P.Lear, Piqua, Ohio, assignor to, Lear Avia, Inc., Piqua, Ohio, acorporation of Illinois Original applications July 27, 1939, Serial No.286,733, and December 28, 1940, Serial No. 372,059. Divided and thisapplication January 18, 1943, Serial No. 472,715

20 Claims. (Cl. 25011) The present invention relates to radio directionfinding systems, and more particularly to automatic radio directionindicators. is a division of my copending applications Serial Numbers372,059 and 286,733 filed on December 28, 1940, and July 27, 1939,respectively, now patents, No. 2,317,922 and 2,308,521, respectively,issued April 27, 1943, and January 19, 1943, respectively, and assignedto the same assignee as this case.

The automatic radio direction finder to which this invention relatesemploys a reversible elec-; tric motor controlled by the received radiosignals for rotating a directional antenna into bearing relationshipwith the incoming radio waves. The directional antenna is generally arotatable loop mounted on the exterior of the aircraft for eflficientsignal reception. A 360 indicator is mechanically coupled to the drivendirectional antenna to indicate its angular position and azimuthalbearing.

In accordance with the present invention, the control motor is arrangedremote from the directional antenna, being incorporated in theelectrical control compartment. As will be set forth in detailhereinafter, locating the control motor within a shielded chassis closeto its electrical control circuits eliminates the electrical cablespreviously used and thereby electrical interfer- This case staticconditions, or manual direction finding is otherwise indicated.

It is also a feature of the invention to include a quadrantal errorcorrector in the motor, manual-drive, loop antenna and indicator systemin a manner insuring bearing indications always in corrected form,whether the loop is positioned automatically or manually.

These and other advantages, capabilities, and

features of the invention will appear from the following detaileddescription of a specific emences with signal reception or the magneticcdm pass. The interference generally was manifest as switching clicksand commutator noise, or other electromagnetic waves radiated by theconnecting cable. Furthermore, the motor is subjected to far lessvariation in temperature than when located adjacent the externallymounted loop antenna as heretofore. The result is a more stableoperation.

A prominent feature of my invention consists in providing an automaticmotor drive for a rotatable loop antenna through appropriate reductiongearing in combination with an independently usable remote manual drivefor the loop antenna. In this connection an electromagnetic clutch,interposed between the motor and its normally associated gearing servesto disconnect the motor automatically from the loop antenna should themotor circuit become inoperative. Manual control of the loop through anormally disengaged clutch permits ready and unencumbered operation ofthe direction finder during such condition of the motor circuit. Also,manual control of the loop antenna is useful when radio reception by theloop during precipitation bodimentthereof, illustrated in theaccompanying drawings, in which: r V Y Fig. 1 is a diagrammaticillustration of the system, in perspective, showing coaction of thecomponents.

Figs. 2, 3 and 4 illustrate diagrammatically further practical forms ofthe system.

The automatic radio directional system, diagrammatically shown in Fig.1, comprises a control unit In, a radio and electrical control circuitunit l5, ,and rotatable directional antenna 20. Antenna 20is a rotatablymounted loop within streamline housing 2| supported on neck 22. Theantennaassembly is arranged on shell 23 of the aircraft, extending aboveor below the aircraft fuselage to insure efiicient pick-up of the radiosignals. The control unit or head In is placed near the pilot forremotely operating the direction finder system.

Chassis unit [5 contains the requisite radio and control circuits forthe system, being generally located remote from the loop antenna, at aconvenient accessible place for its maintenance and servicing. My PatentNo. 2,308,521 referred to hereinabove, discloses appropriate circuitsfor effecting the automatic radio directional operation. A 360 indicator25 is coupled to the direction finder system, being placed near thepilot for indicating the bearing position of loop 29.

A band selector switch 30 is provided on control head In for adjustingthe radio circuits in units I0 and I5 to the desired band of radiofrequency operation. Selector switch 30 simultaneously shifts shuttermask 3| of radio tuning indicator 32in correspondence with the bandselected. Details of this arrangement appear in my copendingapplication, Serial No. 378,490, filed on February 12, 1941, now PatentNo. 2,344,825, issued March 21, 1944. Tuning knob 33 operates aslide-rule type frequency scale 34 to indicate the frequency of theradio station tuned-in opposite stationary index 35. Tuning knob 33 atthe same time rotates mechanical cable 36 coupled to the variable radiofrequency condenser bank within chassis unit 15 for correspondinglytuning the contained direction finder circuits. A tuning meter 31, incircuit with theradio system, ap-

prises the pilot of the optimum tuning conditions.

The mode; of circuit operation for thadiiection finder st m.- s a re leby sw t h ever w t control head [0. The gain level of the system isadjusted by knob 39. The electrical connections, between control headandchassis unit l com prise junction box 40 and electrical cables; 42

Chassis unit l5 contains,a removahlemetallic,

V casing 43 and front panel 44;] Referenceisdi;

rooted to mycopending application Serial No. 354,653, filed on August29, 1 9 4(L now Patent No. 2,309,323 issued January 26;r19jfl-3;for-pref err1ed construction of this unit. t' lhdlion directi naltraneous radio distortions,'in a manner well known in the art.

Besidesindicator-25, there is a second indicator unit 55 containing, aradio bearing index 66. Index. 6.6 isv connected to H-coupling unit 55through mechanicalshaft 61. Indicator 65 coaxially coordinates the radiobearing indications with, thoseoi a gyro-compass within unit 65, in

' the. manner dis losed in my copending applicaantenna 45 is connectedto insulatedterminal' lbi.

on the front of unit I5. The master on-off switch 4! for the directionfinder system is arrangedlorr Pa el 4 4i remotely from contr l head 1.Th power supply for the system is conducted through cabl s 2 and.viaiunction'bo 1-. n; th mann rithe. elatiyelr hiehamneraeeicurrentif rh ystem. does; not ass thrvqu h h airc ait e adja entiheoinstmmentpanel.,thusayo din ny. efiiects n theima netieeem assi.

The p Winding ll soi. low. immdaneaand elect ica ly. ennected. tcradiacirte itunit L5 by lowimnedanee.sh ldedleableia hre h uncti n has. 11:and. ab e. 2 Connec ion. between. table 4%. nd. he; re a a le c n iafforded through slip rings. A quadmmalerror corrector unit 5.0 isreelnledl etweemhe enna ll andm eh nieal heri-til. w i h; perates the loop,in a manner such as indicatedinmy BetentN 293 3643 1 .ies edl ecemb t4,3:a d assigned to helsam ae ie ea.

Le ndrive shait. 5111s. mech nicallsi coupled-r a dr unit, 52 mo nted.panel... 44L oi; chassis nit b flexible hait 53. andshaf 54 (nan-H:- celine, ni 5a Dr ve 52. ineqrp ra s n electromagnetic, lutch.v as will p ent be. explained. shaft,.5.3..is remo ab yeennledtemeto 7 drive unit.52. by, nipple, arrangement. 6 lec:

trical cable 42. isl m ahly. coupledto socket5l n. R nel 44 throughmultipleplugia. control head shaft 36 is,.rem vablyl coupled to panel.4.4 y. ou l g Piece 59.v Chassis... u it. .1 may ac;

cordingly be readily uncoupledboth electrically;

and mecha i a x romv he. ema nder. if t direction findersystemic:greatly-facilitat ng ts mainte a ce. and ervic ng nthe, field-The. loop. drive ys em iswar an ed. n. the con o hassis unit li re otefromthe etatable lo antenna 2.0.. The. motoris. electrical y shieldedbyhousing 43., The, cable connections to. the motor are; Short anddirectland wholly within unit, l5. No motor. circuit, connections. ar requiredzbetween control, unit. 15: the remotely. posi- 0 01 10019 20, t r byaveiclina niexierenee w th aenetia om a aer w t ZhBJ-fidill reee e tieRa ia ien. or. .111 as nd emmui te nemesise m natedt e beloop ant na .2drive n Z-thQl- Eh-,fl ?$lb mechani alham n 5i, 5.3.J'pined etha em n133L552 Bea n -tindicater- .5 mechan al envied a themech mi al 00 d ive.sys m fle ble st it 6.0

c nneet dwithl haft 64- f 'He im hafts. 5. anal- 1. f: .-un.it 5.5.are-eenn c ed y. l. g ari n ic ton shah fill is. accordin ly osii l eated.- it. me ndrive-emit 5 e ow. mg. in, phase; with shaft. 51,, which,controls, the angularposition d. 0 n. n nr1a. fl. Pointer 64 ofindicator is directly geared to shaft 60 in the meeheniea lndri enib ingtherewith by shaft 61.

ti n: serialjNo. 314,672 filed on January 19, 1940, and assigned to thesame assignee. A gear ring supports index 66 and engages with a pinionat 683. in theratio, equal to the gearing between loop antenna 20;anddriveshaft St, for iii-phase driv- The respective mechanicaltransmission shafts-5l, 53, 6D and-t1 are individually removably coupledto H-unit through coupling nipples 69; It is tube understood thatadditionar mechanical coupling units may-beconnectedto-drive shaft 53 orto any of r the individual mechanical drive shafts, for'opertatable loopan I ating additional remoteindicators of" the-'- loop bearingpositions.

The 360quadra-ntal error corrector; BO proi/ided between loop antenna.20 and the plurality-of bearing indicators andmotor driveunit- Staffordaccurate azimuthal bearingindications.atra plurality of positions: on.the aircraft. The indicators are thus individually interchangeable or.-removable, without affecting the operation of-"theremaining-indicators.- Coupling nipples: 69 of H'- ,unit 55' permittheconvenient-addition of anvinsembledfor servicing; the severalindicators; 25

and 6B; remainin inephase relation with the loop antenna 20' andcorrector 5.0; and" need" not: be testedor readjusted after theservicing;

As. alreadyindicated; an important feature of the present invention"resides in connecting; a manual loopv drivecrankfwror any other suitablemanually actuated mechanism. mechanically to indicator l5iandiits-driveshaft: lilhthrougha com nection-J l indicated in :dotted'rlinesl In theevent that manual direction finding operation is; indicated in fli ht,suchzass-whentherelectric, motor eontrel n v 52;.is disco nec d or; inpe tive, direct; drive of loop; 2,0- and; the; associahedj radio indiees6 and 6.6; are e cted throu h crank- '0. Aural or-r visualnull signalreceptionisthen used with the system. According to my'present, in.-vention, 0141 4111 10 is; ;normally-uncglutched from conn ct n-. to-pren t eta n dur ng automa ic; di e ti nal. operati n. radii stina; k abHimcoupled; to ,b. earing .-seale 'l3 ion-displac' it frem ts ind catedeei asitienenever dee ireddu i-rienavi ation;

I n 2, loop antenna; mounted upon rota;t.. able-shaft. H, is shownelectrically connected, t0 theloop transmission cable. Ma -throughbrushes tarengag ing sliprings l2: on-loop shaft H. A worm. and wormgeardrive l4, liter the loop;is co n cted t motor IL throu h-a sp r g aand pinion arrangement. or, train 1' electromaen tiet hii Met r l a d.clutch are onn i dl ot rv rel ys inth mann r partiindicated"gearing-occurs automatically; A- funther rotational control= for-loop-;2Il"-is -provided through" mechanical shaft 2t connected-to handcrank-10 through clutcl-i release=-member-- T l; Flexible mechanical shaft -2fi'ismadesufiiciently long'to-reach the'cockpit; and corresponds' toshaft53 'ofFig; 1;

Wormgearing I4; I 6- has apredetermined=-reductionratio to step down thespeed-of-loop shaft IIfrom tha-tof flexible shaft 265- and a reductionratio -of' 40:1 is 'suflicientfor this -relation- A second reduction isapplied between gears -I4,- I6 and motor I 1 through spur gearing; I 83-I9 which inthe practical embodiment' may have a 10:1 ratio.

Electromagnetic clutch '24" iselectrically operated by the motor controlcircuit/to automatically disengage motor I I fromloop shaft 26 and thedrive gearing; I 8", I 9': Such operation frees shaft ZB-fromthemotoryand releases the latter as'a load from the loop system' whenmanually controlled by crank-W." Inthis connection; itmay be noted thatclutch 1 I normally biases crank"! out ofengagement so that it-willnotturnwhen the loop'is rotated by motor I I. The pilotengages clutch I Iwhen-he desires to manually rotate the loop antenna. Moreover; in-- thisform of the invention, the pointer 64-of-'-mechanical loop positionindicator isdriven --by worm gearing 28, 29 with; worm. 28-"secured'tomechanical shaft 26; A negligible angular; lag by shaft 26 providesaccurate bearing indications through the indicator needle 64; Aquadrantal corrector unit is" inserted inloop shaft' l I between gear I6 and loop' 2H. Quadrantalunitv indicated at 5|] is a mechanicalarrangement for varying or otherwise compensating 'for the angularposition of loop 20 withrespect to drive gear I6 inl-accordance withdetermined electrical bearing-distortions caused *bymetallic structuralcomponents ofthe aircraft? Thus, anyposition in dicatedby needle 64'wi1lbe the correct or com,- pensated bearing correspondingtoanelectrical null or zero position of loop-202' Quadrantal errorcorrector 50"is merely indicated inschematic form and asuitablepreferred construction there- I of isdeScribed in my said PatentNo; 2,336,361;

Fig. 3' shows a furtherform for the combined manualandautomatic loopdrive. In thisiexample; motor drive I? and associatedelectromag neticclutch 24 are. positioned near the hand.- crank-lil in the cockpitremote from loop antenna 20 as indicated-by broken lines .141Reductionspur gearing I8";"'I9' connects'the clutch side of' themotordrive to mechanical shaftj26 through reversible-drive gearing,arrangement 15. Bevel gear 18;, isslidably keyed on shaft. I1 connectedwith gear I8"; forengagement with bevel gear 18 secured to the end offlexible cable 26"; Opposed bevel; gear-19 is secured to crank shaft Bll and is mechanically separate from bevel gear 76;

Spring 8I normally mechanically .biases bevel gear 16 intoengagementwith gear I87 so .thatmotor IT willbe normally effective inrotating loop 20". Should the pilot desire to manually rotate loop 20,.he simply grips the crank.handle..'|0, presses it'inwardly againstbiasingspring flili to disengage the motor drive fromgear ,78 andengage. bevel gear 19, therewith. Direct manual driving control of loop20. is effected .inthis, man.-

jner, d pe d n ly of anyenerei ation of motor I 11.. In this example,.gears, I 8.; I9.'. are, not

driven, and; free manual rotation; of loop, 20 is possible withouthindrance from the motor or the associated gearing thereof-x Manualrotation of loop-antenna ZU' -in the embodiments showmin Figs. 2 and 3'does not entailrotation of motor I]; Furthermore when loop antenna 20isdriven by motor Il the crank handle 'Illis mechanically disconnectedand is not rotated.

An indicator 82- is mechanically connected. to shaft 26 through worm 28"on shaft26l. Worm gear 29 mesheswith worm 28'.- Indicator 82 is coupledto gear 29" through shaft 831 A quadrantal or azimuth compensator isincorporated in-indicator- 82 so that the bearingindicatedjby needle 8%thereof is corrected for quadrantalere rorsn The W0lm:l4i' on shaft26*drives wormclfi' on loop shaftl'l; thus. rotating loop =20 :as.already described.

Still another formfor .the .combined'manual and motor drivearrangementfor rotatable antennalfl is illustrated in'Fig. ,4; Motor' I1: isassociatedwith a multiple: gearing system-185- connected to loop shaft II. The train-of-gearscome prising. system 85 includes spur gearMia-secured to loop shaft II and associated pinion-81 meshing therewithin turn: secured to spurt gear 88 meshing with pinion;89.'-Pinion:89..is: connected to the end of flexible; shaft/-26" extending todashboard 90 of the cockpit. A'further spur gear 9|isnrotatedrigidly-with pinion 89. and coupled to pinion 92 throughintermediate gearing-93, 94-. The clutchlsideof themotor drive is.coupled to pinion fl2rthroughi beveled. gears 95;. 95 The over-all ratioofrgear train;85 between pinion. 92 and loop gear-86 is of, the .orderof :1..ina preferred arrangement; for. substantially increasing the;motor speed for. rotation, of. loop an:- tenna 2.0;.

The manual. drive connection through "crank 10. at dashboard 9.0withgear. train .85.,through flexible. shaft 26' is. effectedat anintermediate section of the gear trainthrough a normally disengagedclutch 91. Thus,.the manual turning effort by crank lll'i'upon loop 20.is at a lower reduction ratio than the motor I! turning. efiort. Clutch91, is schematically shown containing spring 8| biasing crank I0 out ofengagement with clutch 91. When the pilot wishes to manually rotate loop2'0; he presses crank 1U"inwardly against spring 8i" engaging clutch 91'and driving the loop through the intermediate gearing. Motor. I! andclutch 24- are not energized duringthe manual control, and the armatureof motor-I I does not add to the mechanical load ofthe rotating system.I A

A-mechanicalquadrantal error corrector 50 is inserted in shaft Il'between loop 20 andelectric position repeater 98 Electric positionrepeater 98' and associated loop azimuth indicator 99 correspond to atelemetering arrangement not shown herein but fully disclosed in myPatent No. 2,308,521; Abattery I00 energizes the position repeaterunitsinterconnected by cable IIlI. Indications by needle =Ill2" of;indicator 99 correspond to the azimuthal bearings due tothequad rantalerror correctionsv by unit 50". Broken lines IIJ3-.schematicallyindicatea remote position for dash-boardflfi; carrying. crank'lllf' andloopposition indicator. 99L 1 Although I have illustrated. severalembodiments of myinvention, it is to, be understood that variations maybe made falling within the broader principlesaand scope thereof; asdefined .in the-following claims,

What I claim is 1.. In combination with I a rotatalole directionalantenna a reversible electric motor for controlling the rotation of saidantenna; mechanism for manually rotating said antenna comprising acrank, a cable joining said crank with said antenna and a membernormally uncoupling said crank from said cable; and an electromagneticclutch in circuit with said motor mechanically coupling said antenna andmotor when said motor is energized to rotate the antenna and normallyuncoupling said motor from the antenna when the motor is deenergized.

2. In combination with a rotatable loop antenna a reversible electricmotor for controlling the rotation of said antenna; mechanism formanually rotating said antenna comprising a crank, a flexible cablemechanically joining said crank with said antenna and a member normallyuncoupling said crank from said flexible cable;

and an electromagnetic clutch in circuit with said motor mechanicallycoupling said antenna I and motor when said motor is energized toro- 'acrank and a flexible cable for mechanically joining said crank with saidloop antenna, a 360 indicator remotely coupled to said. loop antenna forshowing the angular position thereof, and

a 'quadrantal corrector between said antenna and said indicator forcompensating the indications thereof to give proper directional radiobearings.

4. A radio direction finder system comprising a rotatable directionalantenna, a 360 bearing indicator, a mechanicaldrive for driving ,saidantenna with said bearing indicator, an electric motor coupled to saidmechanical drive for operating said antenna and indicator, an electriccontrol circuit for automatically operating said motor, an electricallycontrolled clutch associatedwith said circuit and disposed between said.motor and mechanical drive for automatically disengaging said motorfrom thelatter when the motor control circuit is deenergized andinactive, and manually actuated means for operating the antenna andindicator during an inactive condition of said motor.

5. A radio direction finder system comprising a-rotatable directionalantenna, a 360 bearing indicator, an electric motor coupled to saidmechanical drive for operating said antenna and indicator, an electriccontrol circuit for automatically operating an electrically controlledclutch associated with said circuit and disposed between said motor andthe antenna and bearing indicator for automatically disengaging the mo-.tor from driving connection with said antennaand bearing indicator whenthe motor circuit is inoperative, a member for manually operating theantenna and indicator during the inactive condition of said motorcontrol circuit, and normally disengaged clutch means coupling saidantenna and indicator with saidmember.

6. A system for rotating a. directional antenna of a radio directionfinding system comprising a 'motor actuated mechanism for rotating saidantenna, a manually actuated mechanism for rotating said antenna, meansfor disconnecting :said motor actuated mechanism and self disengagingmeans for coupling said manually actuated mechanism with said antenna. 1

'7. A system for rotating a directional antenna of a radio directionfinding system comprising. a motor actuated mechanism for rotating saidantenna, a manually actuated mechanism for rotating said antenna, amember for coupling said motor actuated mechanism with said antenna,means for disengaging said coupling and a self disengaging coupling forcoupling said manually actuated mechanism with said antenna.

8. A system for rotating a directional antenna of a radio directionfinding system comprising a driving shaft, a gearing coupling said shaftwith said rotatable antenna, a motor, a member for coupling said motorwith said shaft, means for disengaging said shaft, a manually actuatedmechanism for driving said shaft, means for coupling said manuallyactuated mechanism with said driving shaft and means for normallyuncoupling said manually actuated mechanism.

9. A system for rotating a directional antenna of a radio directionfinding system comprising a motor actuated mechanism for rotating saidantenna, a manually actuated mechanism for rotating said antenna, amember for coupling said motor actuated mechanism with said antenna,means for disengaging said coupling, a self disengaging coupling forcoupling said manually actuated mechanism with said antenna, a reductiongearing between said antenna and said motor actuated mechanism, and asecond reduc mechanism for driving said shaft, means for coupling saidmanually actuated mechanism with said driving shaft and springs biasingsaid coupling means normally into their disengaged position.

11. A system for rotating a directional antenna of a radio directionfinding system comprising a motor actuated mechanism for rotating saidantenna, a manually actuated mechanism for rotating said antenna,gearing for coupling said motor actuated mechanism and said manuallyactuated mechanism with said antenna, said gearing having two positionsone coupling said motor actuated mechanism with said antenna andtheother coupling said manually actuated mechanism with saidantenna,'and means for biasing said gearing into the position inwhich itcouples said motor actuated mechanism with said antenna.

. 12. A system for rotating a directional antenna of a radio directionfinding system comprising a motor actuated mechanism for rotating saidantenna, a manually actuated mechanism for rotatingsaid antenna, gearingfor coupling said motor actuated mechanism and said manually actuatedmechanism with said antenna, said gearing having two positions onecoupling said motor actuated mechanism with said antenna said motoractuated mechanism with said antenna and a clutch for disconnecting saidmotor actuated mechanism provided between said gearing and said motoractuated mechanism.

13. ,A system for rotating a rotatable antenna of a radio directionfinding system comprising a motor actuated mechanism for rotating saidantenna, reduction gearing, including an intermediate section, forcoupling said motor actuated mechanism with said antenna, a manuallyactuated mechanism, a driving shaft, a gearing connecting said drivingshaft with the intermediate section of said reduction gearing and a selfdisengaging member coupling said driving shaft with said manuallyactuated mechanism.

14. A system for rotating a directional antenna of a radio directionfinding "system comprising an electric motor for rotating said antenna,a manually actuated mechanism for rotating said antenna, anelectromagnetic clutch coupling said motor with said antenna,electrically controlled means for disconnecting said clutch should saidmotor become inoperative, and self disengaging mechanical means forcoupling said manually actuated mechanism with said antenna.

15. Asystem for rotating a directional antenna of a radio directionfinding system comprising a motor actuated mechanism for operating saidantenna, a manually actuated mechanism for alternatively operating saidantenna, an indicator for remotely showing the angular position thereofoperatively coupled to said antenna, a quadrantal error correctorbetween said antenna and said indicator to provide proper directionalradio bearings, means for disconnecting said motor actuated mechanism,and a self-disengaging coupling connecting said manually actuatedmechanism with said antenna. 16. A system for rotating a rotatable loopantenna of a radio direction finding system comprising first and secondbearin indicators; a motor actuated mechanism for rotating the antennaand said indicators; a manually actuated mechanism for rotating theantenna and said indicators; a quadrantal error corrector coupled to theantenna to provide proper directional bearings; gearing meansmechanically coupling together said corrector, said motor actuatedmechanism and said indicators; and a. self disengaging coupling forconnecting said manually actuated mechanism to said gearing means.

17. A system for rotating a rotatable loop antenna of a radio directionfinding system comprising first and second bearing indicators; a motoractuated mechanism for rotating the antenna and said indicators; amanually actuated mechanism for rotating the antenna and saidindicators; a quadrantal error corrector coupled to the antenna toprovide proper directional bearings; gearing means mechanically couplingtogether said corrector, said motor actuated mechanism and saidindicators; and a self disengaging coupling for connecting said manuallyactuated mechanism to one of said indicators.

18. A system for rotatin a rotatable loop antenna of a radio directionfinding system comprising first and second bearing indicators; a motoractuated mechanism for rotating the antenna and said indicators; amanually actuated mechanism for rotating the antenna and saidindicators; a quadrantal error the antenna to provide proper directionalbearings; gearing means mechanically coupling together said corrector,said motor actuated mechanism and said indicators; a self disengagingcoupling for connecting said manually actuated mechanism to said gearingmeans; said motor actuated mechanism including an electric motor andclutch means eifective,'upon energization of said motor, to connect thesame to said gear means and, upon deenergization of said motor, todisconnect the same from said gear means; and circuit means responsiveto signals received by the antenna for controlling operation of saidmotor and said clutch means.

19. A system for rotating a rotatable loop antenna of a radio directionfinding system comprising a motor actuated mechanism for rotating theantenna; a manually actuated mechanism for rotating the antenna; aflexible drive shaft connected to the antenna; gearing for coupling saidmotor actuated mechanism and said manually actuated mechanism to theantenna, said gearing having two positions, one coupling said motoractuated mechanism with the antenna and the other coupling said manuallyactuated mechanism with the antenna; means for biasing said gearing intothe position in which it couples said motor actuated mechanism with theantenna; a clutch for disconnecting said motor actuated mechanisminterposed between the same and said gearing; a bearing indicator; gearmeans connecting said indicator to said flexible drive shaft; and aquadrantal error corrector interposed between said indicator and gearmeans to provide proper directional bearings on said indicator.

20. A system for rotating a rotatable loop antenna of a radio directionfinding system comprising a motor actuated mechanism for rotating theantenna; a manually actuated mechanism for rotating the antenna; aquadrantal erroncorrector coupled to the antenna to provide properdirectional bearings; a self disengaging coupling for connecting saidmanually actuated mechanism to the antenna; a clutch for disconnectingsaid motor actuated mechanism interposed between the same and theantenna; a bearing indicator; an electrical position transmitter coupledto said corrector; an electrical position receiver coupled to saidindicator; and circuit means connecting said transmitter to saidreceiver.

WILLIAM P. LEAR.

corrector coupled to

